Competition to provide new and/or improved portable electronic devices continues to increase for both consumer and industrial applications. Consequently, higher density batteries that enable prolonged use and/or higher output power or duration are in high demand. In some applications, it is both desirable and necessary to operate an electronic device at remote locations without access to sources of AC power, such as electrical outlets, generators, or inverters. The inherent unpredictability and variability of conditions in many remote environments, such as variations in humidity, precipitation, and/or elevated ambient temperatures during operation and/or storage of associated batteries, compounded with the volatile chemistry of high-energy battery cells, creates additional challenges with respect to battery pack performance and safety.
A common way of providing battery power to portable devices is through use of detachable battery packs. Battery packs used to power portable electronic devices often employ rechargeable Lithium-ion based battery cells, such as Lithium-ion polymer battery (also known as Li-Poly, Li-Pol, or LiPo) cells. While Lithium-ion based battery cells are well suited for large-capacity battery applications, increasing the energy density within battery cells increases the amount of heat that will be exothermically released when the battery cells are discharged. However, if the rate of heat generated within the battery cells exceeds the rate of heat lost to the environment, the risk of explosion, fire, and the release of hazardous decomposition products increases. Likewise, exposing such a system to elevated external temperatures is equally dangerous. Thus, heat dissipation remains a challenge for high energy density battery packs.
While various approaches to regulate the internal temperature of battery packs are known in the art, these approaches may lead to a reduction in performance and/or an increase in battery pack volume, manufacturing cost, and/or power requirements. For example, some battery packs rely on a temperature feedback shut-off control to regulate the internal temperature of the battery pack. If the internal temperature of the battery pack exceeds the recommended operating temperature, the output of the power supply is automatically adjusted, or the circuit is simply cut off.
Existing battery packs may also rely on forced air and/or liquid cooling systems to reduce internal battery pack temperature. For example, a fan to blow air, or a pump to move cooling fluid, such as an ethylene glycol mixture, may be used to dissipate heat from the battery cells. However, this approach adds volume to the battery pack, increases manufacturing costs, and requires energy to run. While some existing unsealed battery packs have implemented safety valves and/or vents to release heat and/or pressure, these unsealed battery packs may not be safely stored and/or operated in moist environments. Further, if a conventional battery pack fails to dissipate the excess heat at a sufficient rate, there is no secondary safeguard in place to mitigate the effects of catastrophic failure.
Accordingly, there is a need in the art to address the above-described as well as other problems.